There has been known a catheter inserted into the inside of a living body lumen such as a blood vessel or the like and used for carrying out diagnosis of the inside of the lumen by. An example is described in Japanese Unexamined Patent Publication No. 2004-344274.
The catheter described in this document is provided with a catheter main body including a lumen, a tubular guide wire insertion portion which is installed at a distal portion of the catheter main body and into which a guide wire is inserted, and a shaft which is inserted into the lumen of the catheter main body and which includes, at a distal portion thereof, an ultrasound oscillation unit emanating ultrasound. In a state of inserting the guide wire in the guide wire insertion portion, this catheter rotates the shaft which is inserted inside the lumen of the catheter main body around the axis thereof and concurrently, moves the shaft in the proximal direction, thereby making it possible to obtain ultrasound images of a blood-vessel wall.
It is also possible for the catheter described in this patent publication to be used, depending on the procedure, in such a manner that a shaft capable of imaging a blood-vessel wall by emanating light and light-receiving the reflection light thereof is inserted in the catheter main body instead of the shaft having the ultrasound oscillation unit.
Then, in the catheter described in the patent publication, the guide wire inserted into the guide wire insertion portion includes a metal core wire existing from the past, so that in case of carrying out image acquisition optically as mentioned above, light is shut by the guide wire and there arises a shadow, so-called “back shadow”, in the image caused by the aforesaid guide wire as shown in FIG. 10. Consequently, at the portion where the back shadow of the image arises, that portion becomes a blind spot and the blood-vessel wall cannot be imaged. In a situation in which, for example, a lesion portion exists at the aforesaid portion which is not imaged, there is a concern that it may be difficult to visually confirm this lesion portion.